In a mobile communication system, 3rd Generation mobile communication services are conducted. Communication standards applied to a 3rd Generation (3G) mobile communication system include the following, for example. Namely, first there is High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), as well as the combination of the two, High Speed Packet Access (HSPA). Also, there is the successor to HSPA, High Speed Packet Access Plus (HSPA+), as well as 3GPP Long Term Evolution (LTE). Note also that a successor to LTE called LTE-Advanced is also under review.
In such 3rd Generation and newer mobile communication systems, in order to improve spectral efficiency, a single channel is used by multiple users, that is, multiple mobile terminals. In other words, a shared channel is used by multiple users.
In order to enable the use of a shared channel by multiple users, a base station uses scheduling to allocate shared channel resources to data addressed to multiple users. With this shared channel scheduling, data is scheduled in order, starting from data received earlier. In other words, scheduling is conducted on existing data. For this reason, data groups addressed to multiple users that are contemporaneously received and kept in a buffer is scheduled with the same schedule timings. In other words, in the case where multiple mobile terminals are included as the addressees of received data groups, scheduling is conducted for all mobile terminals. Also, with this shared channel scheduling, more frequencies are allocated to users with better reception quality. In other words, for data addressed to a user with better reception quality, more data is transmitted per unit time. Note that fairness among terminals is also considered during frequency allocation.
For example, in the case where data is kept in a buffer for multiple mobile terminals, that is, UEs 1, 2, and 3 at a given scheduling timing, all UEs 1, 2, and 3 become subject to scheduling. Additionally, in the case where UE 1 and UE 2 have the same reception quality but the reception quality of UE 3 is lower than the reception quality of UE 1 and UE 2, frequency with the same bandwidth is allocated to UE 1 and UE 2, as illustrated in FIG. 1. Meanwhile, frequency with a narrower bandwidth than the bandwidth for UE 1 and UE 2 is allocated to UE 3. FIG. 1 is a diagram provided to explain a scheduling method of the related art.
For details, see Japanese Laid-open Patent Publication No. 2010-206316.